Hail Season in North Dakota

Across 1996 to 2025, the middle 80 percent of North Dakota's severe hail days fell between May 29 and Aug 28, and the busiest month was July. The busiest single week is centred on Jul 20. The months carrying at least a twelfth of the year's hail days are May, June, July, August. Those are percentiles of what happened, not a boundary: one hail day in ten fell before that opening date and one in ten after the closing date.

Severe hail, meaning stones of 1 inch or larger, was reported somewhere in North Dakota on 954 separate days over the 30 years from 1996 to 2025, which works out at 32 days a year. Stones of 2 inches or larger, the size the Storm Prediction Center calls significant severe, fell on 246 of those days, or 8.2 a year. Severe hail was reported in 30 of the 30 years.

The largest North Dakota hailstone in this 30 year window measured 5 inches across, which is larger than a softball, and fell in Sioux County on 2010-07-13. That is above the largest rung on NOAA's published hail size ladder, which stops at a 4.5 inch softball, so no updraft figure exists for a stone that big. This is the largest report in the 1996 to 2025 window rather than the North Dakota state record, since the older part of the database contains magnitudes that cannot be right.

about 8 in every 10 North Dakota severe hail reports arrive between noon and 9 pm local standard time, and the single busiest hour is the one beginning at 5 pm. That is a straightforward consequence of how thunderstorms work: the sun heats the ground, the ground heats the air above it, and the updraft that carries a stone high enough to grow is strongest in the afternoon. The database's Central Standard timestamps are converted to each report's own approximate local standard time using its longitude, so this figure is derived here rather than published by SPC.

No. There is no hail specific product. Hail is warned inside the Severe Thunderstorm Warning, which the National Weather Service issues for hail of 1 inch or larger or wind gusts over 58 mph, and each warning carries a tag with the maximum hail size the office expects. This page reads those tags live from api.weather.gov and shows them exactly as issued. A Severe Thunderstorm Watch, by contrast, carries no hail size tag at all, because a watch describes an area where severe storms are possible rather than a storm that is happening.

The data cannot answer that. Severe hail reports across the United States more than doubled between the mid 1990s and 2011 while the number of DAYS carrying a report barely moved, which tells you the change was in reporting rather than in the weather. Chasers, smartphones, social media and a denser spotter network all added reports. That is why every headline number on this site is a count of days, not a count of reports.

Two reasons, both worth knowing. First, these pages count only stones of 1 inch or larger, because the National Weather Service moved its severe hail criterion from 0.75 inch to 1 inch on 5 January 2010 and a statistic spanning that change is not comparable with itself. Second, they count days rather than reports. The Storm Prediction Center is explicit about the limits of its own database: "It should also be noted that these data are used by the NWS for verification purposes and may not accurately reflect all storm events." and "Even through the data are smoothed, severe weather reports cluster around population centers."

The NOAA Storm Prediction Center Severe Weather Database, which is the National Weather Service's own record of severe weather reports and is a US Government work in the public domain. These pages take the hail file, keep the 1996 to 2025 window and every report of 1.00 inch or larger, and count days, months, hours and magnitudes from it. County names come from the US Census Bureau 2020 county code file. Live warnings come from api.weather.gov and are shown verbatim.